Principle: Drum dryer is a type of rotating continuous drying equipment that uses a drum-shaped shell to dry materials. The material to be dried is fed into the drum from one end and is then distributed uniformly over the inside surface of the drum, creating a thin layer. The drum is heated from the inside, and as it rotates, the material is dried as it comes into contact with the heated surface. The dried material is then collected at the other end of the drum.

Construction: A typical drum dryer consists of a large, cylindrical drum, usually made of stainless steel or other heat-resistant material. The drum is supported by two or more rotating trunnion wheels and is rotated by a motor through a gear and chain system. The drum is heated by steam, hot air, or other heat sources, and the temperature is controlled by adjusting the flow rate of the heating medium. The drying process can be carried out in a single pass or multiple passes, depending on the material and the desired degree of drying.

Working: The material to be dried is fed into the drum from one end and is then distributed uniformly over the inside surface of the drum. As the drum rotates, the material is exposed to the heated surface and is dried by a combination of conduction, convection, and radiation heat transfer. The dried material is then collected at the other end of the drum, where it is discharged.

Uses: Drum dryers are commonly used in the food, chemical, and pharmaceutical industries to dry materials such as grains, sugar, salt, chemicals, and pharmaceutical products. They are also used in the paper and pulp industry to dry wood chips and other fibrous materials.

Merits:

  1. High thermal efficiency: Drum dryers have a high thermal efficiency, which means that they can dry materials quickly and efficiently.
  2. Continuous operation: Drum dryers are designed for continuous operation, which makes them ideal for large-scale production.
  3. Versatile: Drum dryers can be used to dry a wide range of materials, including solids, liquids, and slurries.
  4. Low maintenance: Drum dryers have a simple design and require minimal maintenance.

Demerits:

  1. Material limitations: Drum dryers are not suitable for drying materials that are sensitive to high temperatures or that require gentle handling.
  2. High capital cost: Drum dryers are relatively expensive compared to other drying equipment.
  3. Difficult to clean: Drum dryers can be difficult to clean, which can lead to contamination issues if they are not properly maintained.
  4. Fire risk: Drum dryers can be a fire hazard if the temperature is not properly controlled or if the drum is overloaded.